Measuring the Impedance of a UHF Quadloop

 

Quad loop antenna is indeed has a 100ohms impedance at the feed point. I tried to build a UHF version of the quad and sweep its frequency response using my handy antenna analyzer. 

Quad loop needs a quarter wavelength of 75 ohm cable in order to transform its impedance from 100ohms to 50ohms.

---73 de du1vss

DIY 30W Power meter using 10dB Attenuator

 

While browsing the internet I came across a 100W/10dB attenuator resistor with a surprisingly low price. This sparked an idea in my mind - I could potentially use this affordable attenuators as a dummy load. What's more, I could connect a diode across its output to make a simple power meter.

The attenuator serves two purposes. 

1. It could function as dummy load as long as you terminate the output terminal with a 50 ohm load.

2. The rf detector is not subjected to extreme rf power as it is connected after the attenuator output.

Given the above details, I started the project as soon as the parts arrived. I had plenty of 180W/2W resistors in my junk box so I created a dummy load using them. According to my calculations, for a 30W of rf input, the 10dB / 100W resistor should effectively reduce it to approximately 3W and my 4 pieces of 180 ohm/2W resistors can safely dissipate the remaining 3W of power.

1N4148 diode is connected across the attenuator output to sample the amount of power being dissipated by the dummy load resistors. A sensitive 200uA ammeter is used to display the power measurement.

I calibrated my DIY power meter using Diamond SX200 swr/power meter as a reference. During the initial test, it exhibited a broadband characteristic. I conducted measurement validation across a range from 88MHz until 173MHz and observed a pleasant flat response. ---73 de du1vss

Advantech WISE-4220-S231 IoT Wireless Module

Today, I will be sharing the advantages of using IoT devices such as the Advantech WISE-4220-S231 wireless sensor. The  WISE 4220 series is an Ethernet-based wireless  IoT device.  What makes this device particularly useful is that its I/0 module is removable and can be replaced with other variants for different applications. Below are the listing of available I/O module for the WISE-4220 series

1. S231 - built-in temperature and humidity sensors.
2. S214 - 4 analog inputs and 4 digital inputs.
3. S250 - 6 digital inputs, 2 digital outputs and 1 rs-485 input.
4. S251 - 6 digital inputs and 1 rs-485 input.

What we have on-hand is the WISE-4220 with S231 variant. Powering the module is simple. It accepts voltages ranging from 10Vdc to 50Vdc. How convenient is that right? Just wait for a few seconds after powering the module and it will start broadcasting its SSID and ready to accepts WiFi connections. You can use your own cellphone or pc to access the wireless web interface. WISE-4220 can be also configured to connect over a wireless network. Data transmission uses the industry standard TCP Modbus protocol. Accessing the module anywhere is much easier as long as you are within the same network.

---73 de du1vss

DIY Arduino Uno Data Logger

Another great project that you can make with arduino is the datalogger. The basic design of a logger calls for a timer, a memory and converter that will translate analog signals from the sensor into a digital data. Today, all of these components are readily available and cheap too. So here are the things you need.

1. Arduino Uno microcontroller.

    

2. 16 x 2 LCD module.

3. DS1307 RTC module.

4. MicroSD Card module.

Start connecting the modules to the arduino by following the picture below. Take note that LCD module is not included in the wiring diagram.

DA1307 RTC module also uses the A4 and A5 pins of the Arduino for its SCL and SDA line. This leaves A0, A1, A2 and A3 as your remaining analog inputs. Never the less, it is still sufficient for this project.

Above is the picture of my completed datalogger. Sampling time is set every 5 minutes. The LCD displays the current time and data but during a short sampling period, it will display **** to tell the user that analog signals at A0, A1, A2 and A3 has been sampled and logged into the sd card successfully.

Below is the code I wrote for my arduino datalogger.

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <uRTCLib.h>

#include <LiquidCrystal.h>

#include <SPI.h>

#include <SD.h>

File myFile;

uRTCLib rtc;

const int rs = 9, en = 8, d4 = 5, d5 = 4, d6 = 3, d7 = 2;

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

void setup() {

delay (2000);

lcd.begin(16, 2);  //initialize LCD module.

if (!SD.begin(10))   //initialize SD module. Chipselect is 10

{

  lcd.clear();

  lcd.setCursor(0,0);

  lcd.print("SD Init Failed");

  while(1);

}

lcd.print("SD Init Done");

delay(1000);

  #ifdef ARDUINO_ARCH_ESP8266

    URTCLIB_WIRE.begin(0, 2); // D3 and D4 on ESP8266

  #else

    URTCLIB_WIRE.begin();

  #endif

  rtc.set_rtc_address(0x68);

  // Only used once, then disabled

  //  rtc.set(0, 42, 16, 6, 2, 5, 15);

  //  RTCLib::set(byte second, byte minute, byte hour, byte dayOfWeek,

// byte dayOfMonth, byte month, byte year)

  //rtc.set(0, 19, 12, 6, 3, 6, 23);

 

}

void loop()

{

  rtc.refresh();

  lcd.clear();

 

  lcd.setCursor(0, 0);

 

 

  lcd.print(rtc.month());

  lcd.print('/');

  lcd.print(rtc.day());

  lcd.print('/');

  lcd.print(rtc.year());

  lcd.print(' ');

 

  lcd.print(rtc.hour());

  lcd.print(':');

  lcd.print(rtc.minute());

  lcd.print(':');

  lcd.print(rtc.second());

 

  lcd.setCursor(0, 1);

//  lcd.print("DOW: ");

//  lcd.print(rtc.dayOfWeek());

if  (rtc.dayOfWeek() == 1)

{lcd.print("Monday");}

if (rtc.dayOfWeek() == 2)

{lcd.print("Tuesday");}

if (rtc.dayOfWeek() == 3)

{lcd.print("Wednesday");}

if (rtc.dayOfWeek() == 4)

{lcd.print("Thursday");}

if (rtc.dayOfWeek() == 5)

{lcd.print("Friday");}

if (rtc.dayOfWeek() == 6)

{lcd.print("Saturday");}

else if (rtc.dayOfWeek() == 7)

{lcd.print("Sunday");}

  delay(1000);

  ////////////Code for data logger begins here....

  int x = (rtc.minute() % 5); /// minute value is divided by 5,

/// the remainder is stored

                               /// in integer x.

  if (x + rtc.second() == 0)  /// Sampling of the logger.

{

  float voltA0 = (analogRead(A0) * (5.0 / 1023.0));

  float voltA1 = (analogRead(A1) * (5.0 / 1023.0));

  float voltA2 = (analogRead(A2) * (5.0 / 1023.0));

  float voltA3 = (analogRead(A3) * (5.0 / 1023.0));

  myFile = SD.open("Logs.csv", FILE_WRITE);

 

  myFile.print(rtc.month());

  myFile.print('/');

  myFile.print(rtc.day());

  myFile.print('/');

  myFile.print(rtc.year());

  myFile.print(",");

  myFile.print(rtc.hour());

  myFile.print(":");

  myFile.print(rtc.minute());

  myFile.print(",");

  myFile.print(" ");

  myFile.print(" ");

  myFile.print(" ");

  myFile.print(" ");  

  myFile.print(voltA0);

  myFile.print(",");

  myFile.print(voltA1);

  myFile.print(",");

  myFile.print(voltA2);

  myFile.print(",");

  myFile.print(voltA3);

  myFile.println(" ");

 

  myFile.close();

  lcd.setCursor(12, 1);

  lcd.print("XXXX"); ///Prints XXXXXX in the lcd after

  delay(200);        ///recording all the analog channels.

}

else

{

 

}

}

 

---73 de du1vss

Homebrew SWR / Power Meter for HF and VHF

 

A friend is asking if I can fabricate a low-cost SWR/power meter with accurate performance up to  144MHz. One of the designs I have attempted is the modified Bruene directional coupler from Roy Lewallen, W7EL.

The above circuit represents a portion of W7EL's original article. I have extracted only the directional coupler circuit, as we intend to employ an analog 200uA meter for indication.

The toroidal transformers were made from FT37-43 cores, using 10 turns in the secondary winding and a single turn in the primary winding. While wire thickness is not critical, I have opted for #24awg enamel wire for the secondary winding. The two diodes employed are a closely matched pair of 1N4148, and the two resistors are rated at 47 ohms (1/2 watt). Measures have been taken to maintain minimal lead lengths, and the compact PCB housing the circuit is conveniently positioned adjacent to the SO239 connectors.

The meter circuit incorporates toggle switches and calibration trimmers essential for precise meter calibration.

Toggle switch S1 serves the purpose of selecting between forward and reflected power, whereas toggle switch S2 facilitates the choice between power and SWR modes for measurement.

During the calibration process, I am using my Diamond SX200 meter as a reference standard, and my ICOM IC-2200H is employed to verify the power readings for both power meters. Additionally, I have prepared three distinct dummy loads – each with impedance values of 50 ohms, 75 ohms, and 100 ohms respectively. These dummy loads are necessary components for SWR calibration.

Meter calibration using SX200 as reference standard.

Actual dummy load used in the swr calibration.

Testing power response at 88MHz to 108MHz.

Testing the power response from 26MHz to 27MHz.

Testing the power response from 136MHz to 150MHz,

Assembling this project is relatively straightforward for me; however, the calibration process presents challenges. Notably, around 150MHz, there is a noticeable decline in power response. It appears that this might already be pushing the upper limits of my power meter's capabilities. Moreover, I've observed toroid transformer heating, particularly during continuous 60W testing.

I extend my heartfelt gratitude to my friend, Sir Leandro, for placing trust in and providing unwavering support for this undertaking. --- 73 de DU1VSS

Digital Tank Level Meter

At my current workplace, we operate with large tanks designed for storing huge quantities of chocolates. Regrettably, these tanks lack built-in sight glasses, imposing a burden on operators who must climb ladders frequently to gauge tank levels before initiating product transfers from the ball mill. One unfortunate incident occurred previously due to insufficient level awareness, resulting in chocolate overflow atop the tank. In response, we proposed  a solution: constructing a dual-function digital level meter.

Firstly, the meter communicates with the PLC, notifying it when the tank reaches full capacity. This triggers an immediate signal to halt the transfer pump, averting potential overflows.

Secondly, a digital display unit was installed adjacent to the tank, facilitating quick and convenient monitoring of the chocolate product's current level within the tank.

Collaborating with a friend, we divided tasks: he managed sensor mounting fabrication, while I undertook sensor selection and the microcontroller's wiring and programming.

At the heart of this project lies an important hardware component – an IFM photoelectric distance sensor. Operating on the principle of laser light measurement, it generates a standard current output (4-20mA). The sensor boasts a maximum measurement range of 10 meters, aligning perfectly with our tank's height and volume parameters.

The 16 x 2 dot matrix LCD together with the Arduino Uno microcontroller  will take care of the sampling of the analog signal from the sensor, do a simultaneous computation and display the level of the tank in real time.

To start the design we have to measure the dimension of the storage tank so that important values can be set in the sensor. The sensor will be mounted just below the lid  so this will be also the sensor origin.

Start of signal (4mA) will appear at 1,450mm below from the sensor origin and the end of signal (20mA) will be at 250mm below the sensor origin.

Given that the sensor generates a current output, we need to convert this current into a 0-5V range, which is in line with the analog channels' specifications of our microcontroller. To fulfill this task, my chosen approach involves adding a 150 ohm resistor soldered in parallel with the (A0) analog channel of the microcontroller. This configuration effectively transforms the sensor's current output into an analog voltage range spanning from 0.6V to 3.0V.

Pin 1 of the sensor serves as the +24V power input, while the sensor's current output is directed to pin 2. This output will be directly connected to the A0 analog channel of our microcontroller. Pin 4 is a normally closed (NC) contact embedded within the sensor. When the product level exceeds the container's lid, this contact will open, triggering a signal sent to the PLC and prompting the transfer pump to halt. Finally, pin 3 functions as the common ground connection.

The tank's content will be visually reported as a percentage level, which we can achieve through mathematical calculations. Employing the Microsoft Excel application, we can create a chart and derive a linear expression from the sensor's range and the corresponding % level data. This linear expression, representing a calibration curve, will then be utilized by the microcontroller to execute calculations and accurately display the tank's % level.

calibration curve linear expression: Y= 41.667X-25

where Y is the  % Level and X is the analog voltage sampled by the microcontroller at channel A0.

The difference in voltage between the photoelectric distance sensor and the microcontroller is efficiently managed by LM2596 buck down converter. This setup accommodates the sensor's operation at a 24Vdc rail while ensuring the microcontroller operates on a 5Vdc supply. Opting for a linear regulator like the 7805 proves unfeasible in this scenario due to the substantial difference between the input and output voltage levels.

After completing the hardware wiring and testing, our functional level meter is now put to test. Below are the actual pictures taken of the display unit installed near the tank.

 I would like to thank my friend, sir Cliff for helping me complete this project. ---73 de du1vss

Programming TK-3000:M6

My new company just bought 10 pcs of Kenwood TK-3000:M6 radio to help our communication inside the plant but the supplier only provide a single programmed frequency in the channel knob. Another problem arise after we found out that the typical range of this unit is not sufficient to cover the entire plant and the only way to solve the problem is to deploy a repeater.

To begin with my repeater project, I need to construct first a programmer and found some some useful circuit here. "http://www.repeater-builder.com/kenwood/kenwood-software-and-cable-list.html" . I just use 2sc9013 NPN transistor and 1N4148 as required in the schematic.

Using my trusted "ugly construction technique", my programmer is now ready. Few more things needed in order to start programming and these are;

• KPG-137D software from Kenwood
• USB-Serial converter

Some settings in the KPG-137D needs to be set correctly such as the port number assigned in the usb-serial converter and the model / frequency range of the radio.

If you need a copy of the software just drop me a message below. ---73 de du1vss